On May 12, 2005, a 75-foot retaining wall below the garden that faces the Hudson River collapsed, resulting a massive landslide which buried the northbound lanes of the Henry Hudson Parkway and six parked cars. The collapse stopped traffic on the highway for several days, but the clean-up began quickly, and the road re-opened on May 15.[3] However, an entry ramp to the highway remained closed for almost two years. No one was injured. A later study found that the collapse could have been prevented.[4]

Reconstruction of the wall and garden, which had been built in 1925 and supported the complex's lawn, was substantially completed by October 2007, at the cost of $24 million. The access ramp to the Henry Hudson Parkway below the wall was partially reopened in March 2008. All reconstruction on the wall, including the full opening of the access ramp was complete by November 2010.[5]